package com.test.search;

import java.util.Comparator;

public class SearchUtil {

    public static <T extends Comparable<T>> int binarySearch(T[] x, T key) {
        return binarySearch(x, 0, x.length- 1, key);
    }

    // 使用循环实现的二分查找
    public static <T> int binarySearch(T[] x, T key, Comparator<T> comp) {
        int low = 0;
        int high = x.length - 1;
        while (low <= high) {
            int mid = (low + high) >>> 1;
            int cmp = comp.compare(x[mid], key);
            if (cmp < 0) {
                low= mid + 1;
            }
            else if (cmp > 0) {
                high= mid - 1;
            }
            else {
                return mid;
            }
        }
        return -1;
    }

    // 使用递归实现的二分查找
    private static<T extends Comparable<T>> int binarySearch(T[] x, int low, int high, T key) {
        if(low <= high) {
            int mid = low + ((high -low) >> 1);
            if(key.compareTo(x[mid])== 0) {
                return mid;
            }
            else if(key.compareTo(x[mid])< 0) {
                return binarySearch(x,low, mid - 1, key);
            }
            else {
                return binarySearch(x,mid + 1, high, key);
            }
        }
        return -1;
    }
}
